Aliso Canyon Update

Recent & Upcoming Meetings

Friday, April 16, 2021 - Aliso Canyon Monitoring Supplemental Environmental Project – Bidders’ Conference

A Bidders Conference was held on Zoom on Friday, April 16, 2021 at 9:00 AM to provide potential bidders with updates on this Supplemental Environmental Project (SEP) and related Request for proposal (RFP), and to answer questions. Below is a link to the recording of this virtual meeting:

Please contact Dr. Andrea Polidori at (909) 396-3283 or at for further details.

Tuesday, March 9, 2021 - Aliso Canyon Fund Community Meeting

May 12, 2020 Mobile Methane Monitoring

In response to more than 100 odor complaints in the area, South Coast AQMD conducted mobile methane measurements in and around the Porter Ranch Community and within the SoCalGas Aliso Canyon facility. The mobile monitoring showed methane measurements to be within typical background levels. One elevated methane reading was detected inside the SoCalGas facility near the main office area. Further investigation confirmed that this was a short-term peak and was not the result of an ongoing leak or the source of the odor complaints. Results from the mobile monitoring can be found in the Figure below.

mobile monitoring map

February 2020 Analysis of Air Quality

South Coast AQMD staff conducted a short-term analysis of air quality in and around Southern California Gas’s (SoCalGas) Aliso Canyon facility.  The purpose of the analysis was to look at potential air impacts from a previously identified leak located on the hillside on the SoCal Gas property.  Three sampling locations were used (Table 1); one located on the SoCal Gas property near the previously identified leak, and two located downwind and within the community (Figure 1).  Samples collected over a 24-hour period were obtained at each of the three sites on January 25th, February 1st, and February 8th, 2020. South Coast AQMD was sampling for gases such as benzene, toluene, and xylene. Analysis of the samples taken from the three locations did not show any levels of gases above what is normal in ambient air in the South Coast Basin (MATES IV Report).  The complete monitoring results can be found at: Lab Results 

 Table 1: Sampling Locations

Map ID




SoCal Gas Fire Road

34.3116, -118.5462 (lat., long.)


Porter Ridge Park

Muirkirk Dr., Porter Ranch


Castlebay Lane Charter School

19010 Castlebay Ln., Porter Ranch

Figure 1

Map of Sampling Locations

Saddle Ridge Fire Results

On October 14, 2019, South Coast AQMD was notified of a fire at the Aliso Canyon natural gas storage facility. Inspectors were dispatched and joined representatives of the Los Angeles County Fire Department Health Hazardous Materials Division (HazMat), the Division of Oil, Gas & Geothermal Resources (DOGGR), the Department of Public Health, the California Public Utilities Commission (CPUC), and So Cal Gas at the site. The fire was extinguished on October 15.

South Coast AQMD conducted mobile methane measurements and collected air samples in the facility as well as in in the surrounding community. The mobile methane measurements in the community showed levels of methane to be within typical ambient levels (Figure 1). Grab air samples were collected on the facility property (nearby the location of the fire), and in the Porter Ridge Park community (Figure 2). Additional samples were collected from nearby oil and gas operations to characterize potential sources of emissions. Results from these samples include methane and other lighter hydrocarbons (Table 1 and 2).

Both HazMat and SoCal Gas took additional air and soil samples which are undergoing independent testing. South Coast AQMD, along with state and local agencies, will continue to evaluate the situation.

Figure 1

Map 1_PP

Figure 2

Map 2_PP

Laboratory Results

Table 1: Air Samples

Lab ID

Map ID

Sample Date




Tues., October 15, 2019

Collected at fire/leak location



Tues., October 15, 2019

Collected downhill from fire/leak location



Sat., October 19, 2019

Collected at fire/leak location



Sat., October 19, 2019

Collected downhill from fire/leak location



Tues., October 22, 2019

Collected at fire/leak location



Tues., October 22, 2019

Collected at Porter Ridge Park

Table 2: Samples of Possible Sources

Lab ID

Map ID

Sample Date




Sat., October 19, 2019

Transmission gas pipeline.



Tues., October 22, 2019

Standard Sesnon Well #21. Shallow produced gas from western side of facility.



Tues., October 22, 2019

Fernando Fee Well #11. Shallow produced gas from eastern side of facility.



Tues., October 22, 2019

Porter Gathering Tank. Mixed field gas.



Wed., November 6, 2019

Fernando Fee Well #38.Underground storage reservoir gas prior to treatment.

Recent & Upcoming Activities




Aliso Canyon Natural Gas Well Sealed

Southern California Gas Company (SoCalGas) operates the Aliso Canyon natural gas underground storage facility at 12801 Tampa Avenue in Northridge, CA 91326. On October 23, 2015 SoCalGas discovered that Well SS25 used to inject and withdraw natural gas from the underground storage reservoir at their Aliso Canyon facility was leaking.  On February 18, 2016, the California Department of Conservation, Division of Gas and Geothermal Resources (DOGGR) provided notice to the public confirming that Well SS25 at the Aliso Canyon Gas Storage Facility had been successfully sealed.

South Coast Air Quality Management District (South Coast AQMD) and California Air Resources Board (CARB) staff jointly developed a set of criteriaLink to external determine when air quality in the surrounding communities of the Aliso Canyon facility has returned to typical conditions -  a checklist to determine when the air quality is no longer being impacted as a result of the leak.  Click on the following links for information about:

South Coast AQMD staff continues to observe and monitor operations at the Aliso Canyon facility and the surrounding community and to conduct ambient air measurements both within the facility and offsite in Porter Ranch and surrounding communities. 

Additional Air Monitoring and Inspection Activities

On July 31, 2017, SoCalGas (SCG) resumed natural gas injection operations at its Aliso Canyon storage facility.  As one of the conditions for resuming injection activities, aerial measurements of methane emissions from the facility were conducted by a third party contractor earlier that week. Airborne surveys on July 27 and August 3, 2017 revealed the presence of increased methane emissions from the northwest portion of Aliso Canyon.

In response to this finding, starting on July 28, 2017, South Coast AQMD staff from the Office of Compliance & Enforcement and Atmospheric Measurement were dispatched to investigate the cause of these elevated aerial measurements, and mobile methane surveys resumed within and outside of the SCG property line, to include within The Termo Company (Termo), and in the surrounding communities. While inspectors and atmospheric measurements staff detected, identified, and verified repairs of specific leaks from various components at both Termo, and SCG, so far, no obvious emission sources associated with renewed injection operations have been detected by South Coast AQMD staff.  

Mobile surveys in Porter Ranch and other neighboring communities have consistently shown methane readings close to typical ambient levels. South Coast AQMD will conduct additional mobile surveys and follow-up inspections at both Termo, and the SCG Aliso Canyon facility, and in the surrounding communities. Mobile methane survey results and updates are posted on our website.

Final Air Monitoring Results

An Executive Summary and a final technical report summarizing the air monitoring results from all fixed site and mobile measurements conducted by CARB and the South Coast AQMD between October 2015 and June 2017 have been prepared:

Compliance/Enforcement Activities

News Releases


Report odors similar to the sulfur (rotten egg) smell of natural gas to 1-800-CUT-SMOG (1-800-288-7664) or through the On-line Complaint System.  If  you otherwise believe there is a problem related to natural gas, please also contact SoCalGas at 1-800-427-2200.

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